Relation between the Diameter of Steel Wire and the Corrosion Rate in NaCl Aqueous Solution

摘要

In order to clarify wire diameter dependency ofcorrosion rate of steel wires, which have been widely used invarious fields, immersion tests and polarization tests in pH 5.9 andpH 2.5 NaCl solutions were conducted to high carbon steel wireswith 0.1 to 1.0 mm in diameter. It was found that the corrosionrate was largely dependent upon the diameter in both solutions,that is, it increased with the decrease of the diameter. Diffusionlimiting current was observed in both solution, and it also had thesame diameter dependency. Corrosion rate and diffusion limitingcurrent in pH 2.5 solution wee about one order larger than those inpH 5.9 solution. The analysis of diffusion limiting current anddiffusion model for cylinder-shaped wire electrode based on Fick'slaw indicated that corrosion rate was controlled by diffusion ofdissolved oxygen in pH 5.9 solution and that by diffusion ofhydrogen ion in pH 2.5 solution, and that the increase of corrosionrate with the decrease of wire diameter was attributable topromotion of cathodic reduction reaction of dissolved oxygen inthe neutral solution, and that of hydrogen ion in the weak acidsolution, respectively.